Suspension system for steered wheel

ABSTRACT

A suspension system for a steered wheel includes a knuckle for steerably supporting the steered wheel about a king pin axis, and upper and lower arms pivotally supported on a vehicle body and connected at free ends thereof to upper and lower portions of the knuckle, respectively. This suspension system further includes a link mechanism which includes a first substantially vertically extending rod connected to the knuckle at a location more inward of the vehicle body than the king pin axis, and a second rod connected at one end to the first rod and at the other end to at least one of the vehicle body and the lower arm. A resilient device is connected to the link mechanism and adapted to exhibit a resilient force repulsive to the deformation of the link mechanism. Thus, even if the king pin offset is set at a small value, a restoring torque can be sufficiently insured in the steering device when steering through a large steering angle at a low speed.

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION

The field of the present invention relates to a suspension system for a steered wheel of an automobile, and particularly, to an improvement of a suspension system for a steered wheel, comprising a knuckle for steerably supporting the steered wheel about a king pin axis, and upper and lower arms pivotally supported on a vehicle body and connected at free ends thereof to upper and lower portions of the knuckle, respectively.

DESCRIPTION OF THE RELEVANT ART

Such suspension systems for a steered wheel are already known, as disclosed, for example, in Japanese Patent Application Laid-open No. 7608/91.

To reduce the torque steering phenomenon significant in a front engine front wheel drive vehicle, it is desirable to reduce, as much as possible, the king pin offset, i.e., a distance between a point at which the king pin axis intersects a road surface and the center of a grounded surface of a wheel, as viewed from the front of the vehicle body. However, the restoring torque of a steering device when steering through a large steering angle at a low speed of the vehicle is proportional to the king pin offset. For this reason, if the king pin offset is set at a reduced value in the above manner, the restoring torque of the steering device when steering through the large steering angle at the low vehicle speed is liable to be deficient.

There has also been proposed suspension system for a steered wheel, wherein a restoring torque is applied to a steering device by deforming a stabilizer in operative association with the steering device (see Japanese Patent Application Laid-open No. 276812/91).

Such previously proposed suspension system for a steered wheel comprises a ball joint 01 provided on a turnable member (i.e., a strut) steered about a king pin axis K, and a ball joint 03 provided on an arm portion 02₁ of the stabilizer 02, as shown in FIGS. 4A to 4C. The ball joints 01 and 03 are connected to upper and lower ends of a vertically extending pull link (i.e., a connecting rod) 04, respectively. The ball joint 01 with the upper end of the pull link 04 connected thereto is provided at a location offset from the king pin axis K by a distance δ.

If the turnable member is steered leftwardly about the king pin axis, the left ball joint 01 is moved on an arcuate locus, thereby causing the left pull link 04 to be pushed downwardly, so that the arm portion 02₁ of the stabilizer 02 connected to the lower end of the pull link 04 through the ball joint 03 is resiliently deformed in a direction of an arrow a in FIG. 4C. As a result, the left pull link 04 is pushed upwardly by a resilient restoring force of a torsion portion 02₂ deformed in a twisted manner, thereby generating a restoring torque intended to restore the turnable member to its neutral position. At the same time, the right pull link 04 connected to the right ball joint 01 is pulled upwardly, and the arm 02₁ of the stabilizer 02 connected to the lower end of the right pull link 04 is resiliently deformed in a direction of an arrow b in FIG. 4C. As a result, the right pull link 04 is pulled downwardly by the torsion portion 02₂ deformed in the twisted manner, thereby generating a restoring torque intended to restore the turnable member to its neutral position. Therefore, even if the restoring torque of the steering device when steering through a large steering angle at a low speed is reduced, as a result of reduction of the king pin offset to reduce the torque steering phenomenon peculiar to a front wheel drive vehicle, a restoring torque can be generated in the steering device by the resilient restoring force of the stabilizer 02.

However, in practice, as shown in FIG. 4C, the right pull link 04 is pulled upwardly and laterally with the steering of the turnable member, thereby causing the right arm portion 02₁ of the stabilizer 02 to be pulled horizontally (i.e., in a direction of an arrow c), resulting in a disadvantage that the torsion portion 02₂ is not sufficiently deformed in the twisted manner, and hence, no effective restoring torque is generated in the steering device.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a suspension system for a steered wheel, wherein even if the king pin offset is set at a small value, a restoring torque can be insured in the steering device when steering through a large steering angle at a low speed.

To achieve the above object, according to the present invention, there is provided a suspension system for a steered wheel, comprising: a knuckle for steerably supporting the steered wheel about a king pin axis; upper and lower arms pivotally supported on a vehicle body and connected at free ends thereof to upper and lower portions of said knuckle, respectively; a link mechanism including a first vertically extending rod connected to the knuckle at a location more inward of the vehicle body than said king pin axis, and a second rod connected at one end thereof to said first rod and at the other end to at least one of the vehicle body and the lower arm; and a resilient means connected to said link mechanism for exhibiting resilient force repulsive to the deformation of said link mechanism.

With the above construction, if the knuckle is turned about the king pin axis to steer the wheel by the steering device, a resilient repulsive force is accumulated in the resilient means with movement and deformation of the link mechanism, so that a restoring force can be provided to the steering device by the accumulated resilient repulsive force. Thus, even if the king pin offset and the king pin inclination angle of the wheel are set at small values to prevent the torque steering phenomenon, an appropriate restoring force can be generated in the steering device.

Preferably the resilient means may be comprised of a stabilizer extending laterally of the vehicle body with the stabilizer connected at its free end to the second rod, whereby the movement of the knuckle can be transmitted as a vertical displacement (including no horizontal displacement) to the stabilizer, thereby effectively deforming the stabilizer. As a result, a sufficient restoring force can be exhibited by the stabilizer, thereby providing a sufficient restoring torque to the steering device.

According to another preferred aspect of the invention, the resilient means may be comprised of a damper for damping the vertical movement of the knuckle, with the damper connected at its lower end to the knuckle through the first rod and to at least either one of the vehicle body and the lower arm through the second rod the damper can be compressed through the first rod with the turning movement of the knuckle, so that a restoring force can be provided to the steering device by the restoring force of the compressed damper.

According to still another preferred aspect of the invention, the resilient means may be comprised of a suspension spring, the second rod may be formed into an A-shaped arm such that the other end of the second rod is pivotally supported, at two points, to the vehicle body, and the suspension spring may be supported by the link mechanism. Through such arrangement, the suspension spring can be deformed through the link mechanism with the turning movement of the knuckle, so that a restoring force can be provided to the steering device by the restoring force of the deformed suspension spring. In this case, the rigidity of the link mechanism in the longitudinal direction of the vehicle body is increased by forming the second rod into the A-shaped arm which is supported at the two points, and therefore, the link mechanism can be moved vertically without large deflection in the longitudinal direction of the vehicle body to sufficiently deform the suspension spring.

According to still a further preferred aspect of the invention, the resilient means may be comprised of a suspension spring, the first rod may be formed into an I-shaped arm such that the other end of the second rod is pivotally supported, at one point, to the vehicle body; an end of a restraining arm pivotally supported on the vehicle body may be connected to the I-shaped arm, and the suspension spring may be supported by the link mechanism. With this arrangement the suspension spring can be deformed through the link mechanism with the turning movement of the knuckle, so that a restoring force can be provided to the steering device by the restoring force of the deformed suspension spring. In this case, the rigidity of the link mechanism in the longitudinal direction of the vehicle body is increased by reinforcing the I-shaped arm with the restraining arm and, therefore, the link mechanism can be moved vertically without large deflection in the longitudinal direction of the vehicle body to sufficiently deform the suspension spring.

Accordingly to yet another preferred aspect of the invention the resilient means may be comprised of a suspension spring which is supported at one end on the vehicle body and at the other end on a tip end of the first rod, and the suspension spring can be deformed through the first rod with the turning movement of the knuckle, so that an appropriate restoring force can be provided to the steering device by the restoring force of the deformed suspension spring. At this time, the vertical movement of the first rod, as it is, is transmitted to the suspension spring, so that the suspension spring can de deformed sufficiently.

The above and other objects, features and advantages of the invention will become apparent from the following description of preferred embodiments, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of a suspension system for a left front wheel of an automobile according to a first embodiment of the present invention, taken from the rear of a vehicle body;

FIG. 2 is a skeleton diagram corresponding to FIG. 1;

FIG. 3A to 3C are diagrams for explaining the operation of a suspension system, FIG. 3A being a plan diagram, and FIGS. 3B and 3C correspond to views taken from the rear of the vehicle body;

FIG. 4A to 4C are diagrams for explaining the operation of a previously proposed suspension system, FIG. 4A being a plan diagram, and FIGS. 4B and 4C correspond to views taken from the rear of the vehicle body;

FIG. 5 is a view of a suspension system for a left front wheel of an automobile according to a second embodiment of the invention, taken from the rear of a vehicle body;

FIG. 6 is a diagram corresponding to FIG. 5 for explaining its operation;

FIG. 7 is a diagram taken in a direction of line 7--7 in FIG. 6;

FIG. 8 is a view of a suspension system for a left front wheel of an automobile according to a third embodiment of the invention, taken from the rear of a vehicle body;

FIG. 9 is a diagram corresponding to FIG. 8 for explaining its operation;

FIG. 10 is a diagram taken along an arrow 10 in FIG. 9;

FIG. 11 is a view of a suspension system for a left front wheel of an automobile according to a fourth embodiment of the invention, taken from the rear of a vehicle body;

FIG. 12 is a view taken along a line 12--12 in FIG. 11;

FIG. 13 is a skeleton diagram of the suspension system of FIG. 11;

FIG. 14 is a diagram for explaining the operation of the suspension system of FIG. 11;

FIG. 15 is a diagram taken in a direction of line 15--15 in FIG. 14;

FIG. 16 is a skeleton diagram of a suspension system according to a fifth embodiment of the invention;

FIG. 17 is a skeleton diagram of a suspension system according to a sixth embodiment of the invention;

FIG. 18 is a skeleton diagram of a suspension system according to a seventh embodiment of the invention;

FIG. 19 is a skeleton diagram of a suspension system according to an eighth embodiment of the invention;

FIG. 20 is a skeleton diagram of a suspension system according to a ninth embodiment of the invention; and

FIG. 21 is a skeleton diagram of a suspension system according to a tenth embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described by way of several preferred embodiments in connection with the accompanying drawings.

FIGS. 1 to 3 illustrate a first embodiment of the present invention. A right front wheel has the same specularly symmetrical structure as a left front wheel and hence, the illustration of the former wheel is omitted.

Referring to FIGS. 1 and 2, a wheel disk I of a steered wheel W (left front wheel) of a front wheel drive vehicle is coupled at its central portion to a wheel hub 3 together with a brake disk 2. The wheel hub 3 is rotatably supported on a knuckle 4₁ through a ball bearing (not shown).

An upper end of an upper support portion 4_(1u) extending upwardly from the knuckle 4₁ is supported, through a ball joint 8₁, at a tip end of an A-shaped upper arm 7₁ which is pivotally supported on a vehicle body frame B_(F) by means of a pair of rubber bush joints 5₁ and 6₁, with their two base end points spaced apart from each other in a longitudinal direction of a vehicle body. A lower end of a lower support portion 4_(1L) extending downwardly from the knuckle 4₁ is supported, through a ball joint 12₁, at a tip end of an A-shaped lower arm 11₁ which is also pivotally supported on the vehicle body from B_(F) by means of a pair of rubber bush joints 9₁ and 10₁ with their two base end points spaced apart from each other in the longitudinal direction of the vehicle body. A tie rod 13₁ adapted to move laterally in operative association with the operation of a steering wheel is connected at its outer end, through a ball joint 14₁, to a tip end of a steering support portion 4_(1N) extending rearwardly of the vehicle body from a lower portion of the knuckle 4₁. A tip end portion of the lower arm 11₁ and the vehicle body frame B_(F) are interconnected by a suspension spring 16₁ integral with a shock absorber A_(B).

The knuckle 4₁ is vertically movably supported on the vehicle body frame B_(F) with the upper and lower arms 7₁ and 11₁ interposed therebetween, so that a vertical external force supplied from a road surface is absorbed by extension and contraction of the suspension spring 16₁, and a vertical vibration is damped by the shock absorber A_(B). The knuckle 4₁ is steered in a transferred manner about the pair of ball joints 8₁ and 12₁ together with the steered wheel W by the lateral movement of the tie rod 13₁.

In the vicinity of the pair of rubber bush joints 9₁ and 10₁ for supporting the base end of the lower arm 11₁ on the vehicle body frame B_(F) a base end of a lateral link 17₁ as a second rod extending substantially horizontally in a laterally outward direction of the vehicle body is pivotally supported through a rubber bush joint 18₁ for vertically swinging movement. A tip end of the lateral link 17₁ and an intermediate portion of the upper support portion 4_(1u) of the knuckle 4₁ are connected to upper and lower opposite ends of a pull link 19₁ as a first substantially vertically extending rod through ball joints 20₁ and 21₁, respectively. The ball joint 20₁ is offset by a distance 8 in a laterally inward direction of the vehicle body with respect to a king pin axis K₁ (see FIG. 1) which connects the ball joint 8₁ at the tip end of the upper arm 7₁ with the ball joint 12₁ at the tip end of the lower arm 11₁. Therefore, when the knuckle 4₁ is turned laterally about the king pin axis K₁ by the transferred steering, the ball joint 20₁ at the upper end of the pull link 19₁ is moved to describe an arcuate locus (see FIG. 3A). It should be noted that the lateral link 17₁ and the pull link 19₁ constitute a link mechanism 27₁ according to the present invention.

As a result of appropriate setting of the inclination angle of the king pin axis K₁, a distance between the king pin axis K₁ and the center of a grounded surface of the steered wheel W at a level of a wheel center, i.e., a king pin offset 0 (see FIG. 1) is small, thereby providing a reduction in torque steering phenomenon peculiar to the front wheel drive vehicle.

Referring also to FIGS. 3A and 3B, a stabilizer 22 includes a pair of arm portions 22₁, 22₁ flexed forwardly in positions laterally spaced from each other, and a torsion portion 22₂ connected at its left and right opposite ends to the arm portions and extending in the lateral direction of the vehicle body. The torsion portion 22₂ is resiliently supported on the vehicle body frame B_(F) by two supports 23, 23 and free ends of the arm portions 22₁, 22₁ are tip end portions connected to the lateral links 17₁, 17₁ through rubber bush joints 24₁, 24₁.

The stabilizer 22 does not serve as a torsion bar when the left and right steered wheels W, W are moved vertically in the same phase, but it serves as a torsion bar to increase the roll rigidity of the suspension system when the left and right steered wheels W, W are moved vertically in opposite phases.

The operation of the first embodiment of the present invention having the above-described construction will be described below.

Referring to FIG. 1, when the tie rod 13₁ is pushed and pulled laterally of the vehicle body by the operation of the steering wheel, the knuckle 4₁ supporting the steered wheel W is steered laterally about the king pin axis K₁ which connects the ball joint 8₁ at the tip end of the upper arm 7₁ with the ball joint 12₁ at the tip end of the lower arm 11₁. At that time, a restoring torque of the steering device tends to be deficient, particularly when steering through a large steering angle at a low speed, because the king pin offset 0 is set at a small level to reduce the torque steering phenomenon. However, this restoring torque is insured by the present invention in the following manner:

When the steered wheel W is steered, for example, in a leftward direction as viewed in FIG. 3C in order to swing the vehicle, each of the ball joints 20₁ provided on the upper support portions 4_(IU) of the left and right knuckles 4₁ is moved about the king pin axis K₁ from an N position (neutral position) to an L position (left steered position) to describe an arcuate locus. This causes the left lateral link 17₁ to be pushed down in a direction of an arrow a about the rubber bush joint 18₁ by the pull link 19₁ connected to the ball joint 20₁ (see FIG. 3C). As a result, the torsion portion 22₂ of the stabilizer 22 with the arm portions 22₁, 22₁ connected to the left and right lateral links 17₁, 17₁ is twisted at its opposite ends in opposite directions, and is resiliently deformed.

When the stabilizer 21₂ is resiliently deformed in this manner, a restoring force thereof allows the knuckle 4₁ and thus the steered wheel W to be biased toward the neutral position (N position) and hence, a restoring torque can be generated in the steering device. At that time, the movement of the left and right pull links 19₁, 19₁ is transmitted as a vertical displacement to the arm portions 22₁, 22₁ of the stabilizer 22, while being restrained by the lateral links 17₁, 17₁ which are pivotally supported on the vehicle body frame B_(F), so that only the vertical swinging movement thereof is permitted. Thus, the torsion portion 22₂ of the stabilizer 22 can be effectively deformed to generate a sufficient restoring force. Therefore, the stabilizer 22 corresponds to a resilient means in this embodiment of the present invention.

When the steered wheel W is steered in the reverse direction, i.e., in a rightward direction, each of the ball joints 20₁ provided on the upper support portions 4_(IU) of the left and right knuckles 4₁ is moved about the king pin axis K₁ from the N position (neutral position) to an R position (right steered position) to describe an arcuate locus. This causes the left and right lateral links 17₁ to be swung in the reverse direction from that described above to deform the torsion portion 22₂ of the stabilizer 22 in a twisting manner, so that a restoring torque can be generated in the steering device.

In the first embodiment of the present invention as shown, the stabilizer 22 is disposed on a rear side of the vehicle body with respect to the lateral link 17₁. Alternatively, the stabilizer 22 may be disposed, for example, on a front side of the vehicle body. In addition, the lateral link 17₁ can be pivotally supported in the vicinity of the base end of the lower arm 11₁, instead of being pivotally supported on the vehicle body frame B_(F). Further, the pull link 19₁ can be connected at its lower end to the knuckle 4₁ and at its upper end to the lateral link 17₁ by vertically reversing the pull link 19₁.

FIGS. 5 to 7 illustrate a second embodiment of the present invention. In this second embodiment, the present invention is applied to a case where both of the king pin offset and the king pin inclination angle are set to be zero, unlike the first embodiment. However, it will be understood that the king pin offset and the king pin inclination angle are not strictly limited to zero according to this embodiment.

As shown in FIGS. 5 to 7 a wheel hub 3 is spline-connected to an outer end of a wheel driving axle A_(D) driven by a power unit (not shown) and is secured thereto by a nut 25. A wheel disk 1 and a brake disk 2 in a wheel W are commonly clamped to a flange 3₁ of the wheel hub 3.

Integrally formed on a knuckle 4₂ supported around an outer periphery of the wheel hub 3 with a ball bearing 26 interposed therebetween are a downwardly extending lower support portion 4_(2L), an upwardly extending upper support portion 4_(2U), steering support portion 4_(2N) extending forwardly of the vehicle body, and a controlling support portion 4_(2C) extending inwardly of the vehicle body from an intermediate portion of the upper portion 4_(2U). A lower arm 11₂ supporting a lower portion of the knuckle 4₂ is pivotally supported at its bifurcated base end on the vehicle body frame B_(F) through a pair of rubber bush joints 9₂ and 10₂, and is pivotally supported at its tip end on the lower support portion 4_(2L) of the knuckle 4₂ through a ball joint 12₂. An upper arm 7₂ supporting an upper portion of the knuckle 4₂ is pivotally supported at its bifurcated base end on the vehicle body frame B_(F) through rubber bush joints 5₂ and 6₂ and is pivotally supported at its tip end on the upper support portion 4_(2U) of the knuckle 4₂ through a ball joint 8₂. The knuckle 4₂ is vertically movably supported on the vehicle body frame B_(F) through the lower arm 11₂ and the upper arm 7₂. In the structure of the second embodiment a king pin axis K₂ connecting the ball joint 12₂ at the lower support portion 4_(2L) of the knuckle 4₂ with the ball joint 8₂ at the upper support portion 4_(2U) is located in a rotational plane of the steered wheel W and hence, both of the king pin offset and the king pin inclination angle of the steered wheel W are set to be zero.

The steering support portion 4_(2N) of the knuckle 4₂ is connected to a steering wheel (not shown) through a tie rod 13₂, whereby the knuckle 4₂ is permitted to be rotated leftwardly and rightwardly about the king pin axis K₂ to steer the steered wheel W.

A damper 16₂ suspending the steered wheel W is connected at its upper end to the vehicle body frame B_(F) and at its lower end to the knuckle 4₂ and the lower arm 11₂ through two rods 19₂ and 17₂. More specifically, a ball joint 20₂ provided at the controlling support portion 4_(2C) of the knuckle 4₂ and a rubber bush joint 21₂ provided at the lower end of the damper 16₂ are interconnected by the first rod 19₂ disposed substantially vertically, and a rubber bush joint 18₂ provided in the vicinity of the base end of the lower arm 11₂ and a rubber bush joint 24₂ provided at the lower end of the damper 16₂ are interconnected by the second rod 17₂ disposed substantially horizontally. With such structure the position of the ball joint 20₂ connecting the controlling support portion 4_(2C) of the knuckle 4₂ with the first rod 19₂ is offset inwardly of the vehicle body from the king pin axis K₂, as clearly shown in FIG. 6 and 7, and is also offset rearwardly of the vehicle body from the center of the steered wheel W, as can be seen from FIG. 7. It is noted here that the first rod 19₂ and the second rod 17₂ constitute a link mechanism 27₂ of the present invention through a lower end of the damper 16₂.

The operation of the second embodiment of the present invention having the above-described construction will be described below.

As is apparent from FIGS. 5 and 6, since the king pin axis K₂ connecting the ball joint 12₂ at the lower support portion of the knuckle 4₂ and the ball joint 8₂ at the upper support portion 4_(2U) lies within a vertical plane passing the center of the steered wheel W, both of the king pin offset and the king pin inclination angle of the steered wheel W are set to be zero. Therefore, even if a torque is transmitted from the steered wheel as a driven wheel to a road surface, the generation of a so-called torque steering phenomenon (through which the steered wheel W is steered in an undesired direction by such torque) is prevented.

In general, however, if both of the king pin offset and the king pin inclination angle of the steered wheel W are set to be zero, the restoring torque of the steering device tends to be deficient when the tie rod 13₂ is pushed and pulled to steer the steered wheel W laterally. This tendency is significant, particularly when steering through a large steering angle at a low speed. With the suspension system of the second embodiment, however, sufficient restoring torque of the steering service can be generated in the following manner:

When the lefthand steered wheel W which is an outer wheel during a turning operation of the vehicle is steered in a direction of an arrow a in FIG. 7 to swing the vehicle, for example, in a rightward direction, the knuckle 4₂ is rotated clockwise about the king pin axis K₂, so that the ball joint 20₂ provided on the controlling support portion 4_(2C) projecting inwardly of the vehicle body from the king pin axis K₂ is displaced rearwardly and outwardly of the vehicle body, as shown by a dashed line in FIGS. 6 and 7. As a result, the lower end of the damper 16₂ is pulled upwardly by the first rod 19₂ which connects the ball joint 20₂ on the controlling support portion 4_(2C) with the rubber bush joint 21₂ on the damper 16₂, and the damper 16₂ is slightly compressed. If the damper 16₂ is compressed in this manner, the steered wheel W is biased, by the steering device, toward the neutral position before the steering operation is complete and therefore, sufficient restoring torque can be generated in the steering device. Thus, the damper 16₂ corresponds to a resilient means in the second embodiment of the present invention.

When the steered wheel W which is an inner wheel during a turning operation of the vehicle is steered in a direction of an arrow b in FIG. 7 to swing the vehicle in the opposite direction, i.e., in a leftward direction, the ball joint 20₂ is displaced forwardly of the vehicle body and also slightly inwardly of the vehicle. However, such displacement of the ball joint 20₂ causes the first rod 19₂ to move little vertically and consequently, substantially no expansion and contraction of the damper 16₂ is performed.

Thus, when the steered wheel is steered to turn the vehicle, the restoring torque is generated in the steered wheel W which is the outer wheel during a turning operation of the vehicle, but such restoring torque is not generated in the steered wheel which is the inner wheel during the turning operation. However, a large load is applied to the outer wheel by a centrifugal force applied to the vehicle during the turning operation, whereas only a small load is applied to the inner wheel. Therefore, the restoring torque generated in the outer wheel acts effectively, and in general, it is possible to apply a sufficient restoring torque to the steering device.

In the above-described second embodiment, the controlling support portion 4_(2C) of the knuckle 4₂, the first rod 19₂, the damper 16₂ and the second rod 17₂ are offset rearwardly of the vehicle body from the center of the steered wheel W in order to avoid the interference with the wheel drive shaft A_(D). In a rear wheel drive vehicle having no wheel drive shaft A_(D), however, these components can be disposed at the longitudinal center of the steered wheel. If they are disposed in this manner, the damper 16₂ can be compressed through the first rod 19₂ regardless of whether the associated steered wheel W is the outer wheel or the inner wheel, and regardless of whether the steered wheel W is steered in either of the leftward and rightward directions. Therefore, it is possible to generate a restoring torque in both of the outer and inner wheels during the turning operation.

In place of provision of the rubber bush joint 18₂ on the lower arm 11₂, the rubber bush joint 18₂ may be provided on the vehicle body frame B_(F). In this case, it is desirable to use a ball joint, because the swinging angle is larger.

A third embodiment of the present invention will now be described in connection with FIGS. 8 to 10. The same components or parts as in the second embodiment are designated by like reference characters, and the detailed description thereof is omitted.

The third embodiment has a distinguishing feature in the structures of an upper support portion 4_(3U) of a knuckle 4₃ and upper arms 7_(3F) and 7_(3R) which connect the upper support portion 4_(3U) with the vehicle body frame B_(F), as compared with the above-described second embodiment. More specifically, the upper support portion 4_(3U) of the knuckle 4₃ in the third embodiment extends around the steered wheel W to a position above the steered wheel W, and the two front and rear upper arms 7_(3F) and 7_(3R) connected respectively to two ball joints 8_(3F) and 8_(3R) provided at an upper end of the upper support portion 4_(3U) are pivotally supported on the vehicle body frame B_(F) through rubber bush joints 5₃ and 6₃, respectively. Further, a second rod 17₃ is pivotally supported on the vehicle body frame B_(F) through a ball joint 18₃. A first rod 19₃ and the second rod 17₃ constitute a link mechanism 27₃ , as in the first embodiment.

As can be seen from FIG. 10, extensions of the two upper arms 7_(3F) and 7_(3R) in an outward direction of the vehicle body intersect each other on a center line of the steered wheel W, and such intersection is a phantom steering center 8_(3i). Therefore, the steered wheel W is steered about a king pin axis K₃ which connects a ball joint 12₂ on a lower support portion 4_(3L) of the knuckle 4₃ with the phantom steering center 8_(3i). The king pin axis K₃ lies within a vertical plane passing the center of the steered wheel W as in the second embodiment and therefore, even if both of the king pin offset and the king pin inclination angle become zero, the generation of a torque steering phenomenon is prevented. Moreover, since the upper support portion 4_(3U) extends above the steered wheel W, the need for accommodating the upper arms 7_(3F) and 7_(3R) within a narrow internal space in a wheel disk 1 is eliminated, thereby enabling an increase in degree of freedom of design. The upper arms 7_(3F) and 7_(3R) are provided in a bisected manner and therefore, outer ends of the upper arms 7_(3F) and 7_(3R) can be moved inwardly of the vehicle body relative to the phantom steering center 8_(3i) to prevent interference with a fender.

Even in the third embodiment, with the steering of the steered wheel W, which is an outer wheel during turning of the vehicle, in a direction of an arrow a (in FIG. 10), the first rod 19₂ can be pulled upwardly to compress the damper 16₂, and a restoring force can be generated in the steering device by a restoring force of the damper 16₂.

In this embodiment, the second rod 17₃ is pivotally supported on the vehicle body frame B_(F) through the ball joint 18₃. Alternatively, it may be pivotally supported on the lower arm 11₂ through a rubber bush joint, as in the second embodiment, in order to suppress the swinging angle. In addition, only the upper arms 7_(3F) and 7_(3R) are of a double joint type in this embodiment, but lower arm 11₂ may also be of a double joint type.

FIGS. 11 to 15 illustrates a fourth embodiment of the present invention. A right front wheel has the same specularly symmetrical structure as a left front wheel and hence, the illustration thereof is omitted.

As shown in FIGS. 11 to 13, a wheel disk 1 in a steered wheel W (a left front wheel ) of an automobile is coupled at its central portion to a wheel hub 3 together with a brake disk 2, and the wheel hub 3 is rotatably supported on a knuckle 4₄ through a ball bearing which is not shown.

A pair of front and rear lower branch arms 4_(4LI) and 4_(4L2) bifurcated inwardly in a widthwise direction of the vehicle body are integrally formed on a lower portion of the knuckle 4₄, and a pair of upper branch arms 4_(4U1) and 4_(4U2) bifurcated to extend upwardly from an inner surface of the steered wheel W are integrally formed on an upper portion of the knuckle 4₄. A steering support portion 4_(4N) is also integrally formed on the knuckle 4₄ to extend rearwardly of the vehicle body.

The pair of front and rear lower branch arms 4_(4L1) and 4_(4L2) of the knuckle 4₄ are connected to the vehicle body frame B_(F) through lower arms 11_(4F) and 11_(4R) which are of a double joint type. More specifically, the front lower arm 11_(4F) is pivotally supported at its outer end on the front lower branch arm 4_(4L1) through a ball joint 12_(4F) and at its inner end on the vehicle body frame B_(F) through a rubber bush joint 9₄. The rear lower arm 11_(4R) is pivotally supported at its outer end on the rear lower branch arm 4_(4L2) through a ball joint 12_(4R) and at its inner end on the vehicle body frame B_(F) through a rubber bush joint 10₄.

The pair of front and rear upper branch arms 4_(4U1) and 4_(4U2) of the knuckle 4₄ are connected to the vehicle body frame B_(F) through upper arms 7_(4F) and 7_(4R) which are of a double joint type. More specifically, the front upper arm 7_(4F) is pivotally supported on the front upper branch arm 4_(4U1) through a ball joint 8_(4F) and at its inner end on the vehicle body frame B_(F) through a rubber bush joint 5₄. The rear upper arm 7_(4R) is pivotally supported at its outer end on the rear upper branch arm 4_(4U2) through a ball joint 8_(4R) and at its inner end on the vehicle body frame B_(F) through a rubber bush joint 6₄.

The knuckle 4₄ is vertically movably supported on the vehicle body frame B_(F) through the pair of front and rear lower arms 11_(4F) and 11_(4R) and the pair of front and rear upper arms 7_(4F) and 7_(4R). In such structure a straight line connecting an intersection 8_(4iL) between the pair of front and rear lower arms 11_(4F) and 11_(4R) extended outwardly in the widthwide direction of the vehicle body with an intersection 8_(4iU) between the pair of front and rear upper arms 7_(4F) and 7_(4R) extended outwardly in the widthwise direction of the vehicle body constitutes a phantom king pin axis K₄ of the steered wheel W (see FIG. 13). This king pin axis K₄ lies within a rotational plane for the steered wheel W and hence, both of the king pin offset and the king pin inclination angle of the steered wheel W are set to be zero (see FIG. 11).

The steering support portion 4_(4N) of the knuckle 4₄ is connected at its tip end to a tie rod 13₄ through a ball joint 14₄, whereby the knuckle 4₄ is permitted to be rotated leftwardly and rightwardly about the king pin axis K₄ to steer the steered wheel W.

A suspension spring 16₄ comprising a coil spring integrally formed on a shock absorber for suspending the steered wheel W is supported at its upper end on the vehicle body frame B_(F) through a rubber bush joint and at its lower end by a suspension spring supporting means 27₄ serving as a link mechanism which comprises a pull rod 19₄ as a first rod and an A-shaped arm 17₄ as a second rod. More specifically, an outer end of the pull rod 19₄ extending upwardly is pivotally supported to a ball joint 20₄ provided at a branch portion of the pair of front and rear upper branch arms 4_(4U1) and 4_(4U2) of the knuckle 4₄, and an inner end of the pull rod 19₄ located below the outer end is pivotally supported to an outer end of the A-shaped arm 17₄ through a rubber bush joint 21₄. The A-shaped arm 17₄ is pivotally supported at its bifurcated inner ends to the vehicle body frame B_(F) through rubber bush joints 18_(4F) and 18_(4R), respectively. The suspension spring 16₄ is pivotally supported at its lower end to a lower portion of the pull rod 19₄ through rubber bush joint 24₄. As can be seen from FIG. 11, the ball joint 20₄ connecting the knuckle 4₄ with the pull rod 19₄ is provided at a location offset inwardly in the widthwise direction of the vehicle body from the king pin axis K₄ by a distance D.

The operation of the fourth embodiment having the above-described construction will be described below.

As can be seen from FIGS. 11 and 13, the king pin axis K₄ connecting the intersection 8_(4iL) between the pair of front and rear lower arms 11_(4F) and 11_(4R) extended outwardly in the widthwise direction of the vehicle body with the intersection 8_(4iU) between the pair of front and rear upper arms 7_(4F) and 7_(4R) extended outwardly in the widthwise direction of the vehicle body is located within a vertical plane passing the center of the steered wheel W and for this reason, the king pin offset and the king pin inclination angle are zero. The deficient tendency of restoring torque of the steering device due to this setting is eliminated in this embodiment in the following manner:

Referring to FIGS. 14 and 15, when the steered wheel W is steered leftwardly or rightwardly to swing the vehicle, the knuckle 4₄ is rotated counterclockwise or clockwise about the king pin axis K₄ and hence, the ball joint 20₄ provided at the location offset inwardly in the widthwise direction of the vehicle body from the king pin axis K₄ is moved from a point P to a point P'. As a result, the ball joint 21₄ connecting the pull rod 19₄ with the A-shaped arm 17₄ is moved from point Q to a point Q', and the rubber bush joint 24₄ connecting the pull rod 19₄ with the suspension spring 16₄ is moved from a point R to a point R', so that the pull rod 19₄, the A-shaped arm 17₄ and the suspension spring 16₄ are brought from states shown by solid lines into states shown by dashed lines in FIGS. 14 and 15. As can be seen from FIG. 14, the rubber bush joint 24₄ at the lower end of the suspension spring 16₄ is moved upwardly from the point R toward the point R', so that the suspension spring 16₄ is compressed by leftward or rightward steering. If the suspension spring 16₄ is compressed in this manner, the steered wheel W is biased toward the neutral position before the steering operation is completed by a restoring force thereof and hence, a restoring torque can be generated in the steering device. Thus, the suspension spring corresponds to the resilient means in this embodiment according to the present invention.

Since the A-shaped arm 17₄ is pivotally supported on the vehicle body frame B_(F) through the two rubber bush joints 18_(4F) and 18_(4R), the rubber bush joint 21₄ to which the lower end of the pull rod 19₄ is connected is movable only in the vertical direction, and movement in the longitudinal direction of the vehicle body is restrained. Consequently, the pull rod 19₄ can be moved vertically without large deflection in the longitudinal direction of the vehicle body and as a result, the pivotal movement of the knuckle 4₄ caused by the steering of the steered wheel W can be converted into the vertical movement of the pull rod 19₄ to compress the suspension spring 16₄, thereby generating a sufficient restoring torque in the steering device.

FIG. 16 illustrate a skeleton diagram of a fifth embodiment and is similar to FIG. 13. the same components or parts as those in FIG. 13 are designated by the same reference characters, and the detailed description thereof is omitted.

In the fifth embodiment, in place of the pair of front and rear lower arms 11_(4F) and 11_(4R) and the pair of front and rear upper arms 7_(4F) and 7_(4R) used in the fourth embodiment, an A-shaped lower arm 11₅ and an A-shaped upper arm 7₅ are included and pivotally supported at their outer ends on a knuckle 4₅ on a king pin axis K₅ through ball joints 12₅ and 8₅. In the fifth embodiment, the king pin offset cannot be set at zero, but by setting the king pin offset at an extremely small value, the substantially same effect of operation as any of the previously-described embodiments can be obtained.

FIG. 17 illustrates a sixth embodiment of the present invention and is similar to FIG. 16. The same components or parts as those in FIG. 16 are designated by the same reference characters, and the detailed description thereof is omitted.

In the sixth embodiment, lower arms 11_(6F) and 11_(6R) of a double joint type and an A-shaped upper arm 7₆ are provided, and a suspension spring supporting means 27₆ as a link mechanism includes an I-shaped arm 17₆ provided in place of the A-shaped arm 17₄ used in the fourth embodiment and is pivotally supported at its opposite ends on the pull rod 19₄ and the vehicle body frame B_(F) through rubber bush joints 21₆ and 18₆. An intermediate portion of the I-shaped arm 17₆ is connected to an end of a stabilizer 22₆ as a restraining arm through a ball joint 28. According to the sixth embodiment, the I-shaped arm 17₆ is reinforced by the stabilizer 22₆ to provide an increased rigidity in the longitudinal direction of the vehicle body. Therefore, as does the A-shaped arm 17₄ in the fourth and fifth embodiments, a deflection of the lower end of the suspension spring 16₄ in the longitudinal direction of the vehicle body can be prevented, and sufficient restoring torque can be generated in the steering device.

FIG. 18 illustrates a seventh embodiment of the present invention and is similar to FIG. 16. The same components or parts as those in FIG. 16 are designated by the same reference characters, and the detailed description thereof is omitted.

The seventh embodiment has a feature that the lower end of the suspension spring 16₄ is supported on an A-shaped arm 17₇ rather than on the pull rod 19₄ through a rubber bush joint 24₇. According to the seventh embodiment, the lower end of the suspension spring 16₄ is moved vertically without deflection in the longitudinal direction of the vehicle body and therefore, the suspension spring 16₄ can be compressed further effectively to generate a sufficient restoring torque in the steering device.

FIG. 19 illustrates an eighth embodiment of the present invention and is similar to FIG. 16. The same components or parts as those in FIG. 16 are designated by the same reference characters, and the detailed description thereof is omitted.

The eighth embodiment has a feature that the A-shaped arm 17₄ is pivotally supported on a rear lower arm 11₈ through rubber bush joints 18₇ and 18₈ in place of being pivotally supported on the vehicle body frame B_(F). According to the eighth embodiment, the number of joints provided on the vehicle body frame B_(F) can be reduced to provide a simplified structure, and a space within a wheel house can be effectively utilized to provide an increased degree of freedom in design.

FIG. 20 illustrates a ninth embodiment of the present invention and is similar to FIG. 16. The same components or parts as those in FIG. 16 are designated by the same reference characters, and the detailed description thereof is omitted.

In the ninth embodiment, the intermediate portion of the pull rod 19₄ and the vehicle body frame B_(F) are interconnected by a simple shock absorber 16₈ having no suspension spring, and a base end of one of the branches of the A-shaped arm 17₄ and the vehicle body frame B_(F) are interconnected by a suspension spring 16₉ comprising a torsion bar disposed to extend longitudinally of the vehicle body. According to this embodiment, a twisting can be applied to the suspension spring 16₉ comprising the torsion bar as a result of vertically swinging movement of the A-shaped arm 17₄ caused by steering, and a restoring torque can be generated in the steering device by a resilient force of the suspension spring 16₉. The degree of freedom in layout can be increased by separating the shock absorber 16₈ and the suspension spring 16₉ from each other.

FIG. 21 illustrates a tenth embodiment of the present invention and is similar to FIG. 16. The same components or pans as those in FIG. 16 are designated by the same reference characters, and the detailed description thereof is omitted.

In the tenth embodiment, the intermediate portion of the pull rod 19₄ and the vehicle body frame B_(F) are interconnected by a shock absorber 16₁₀, and the lower end of the pull rod 19₄ and the vehicle body frame B_(F) are interconnected by a suspension spring 16₁₁ comprising a leaf spring in place of the A-shaped arm 17₄ used in the fifth embodiment. The spring 16₁₁ can be flexed vertically by the vertical movement of the pull rod 19₄ caused by steering, and a restoring torque can be generated in the steering device by a resilient force of the suspension spring 16₁₁. The number of parts and the space is desirably reduced by providing the suspension spring 16₁₁ with a function of the A-shaped arm 17₄, and the suspension is still effective because the vertical movement of the pull rod 19₄ is transmitted as it is, to the suspension spring 16₁₁ and therefore, a large restoring torque can be provided.

The above-described fourth to tenth embodiments of the present invention are also applicable to a suspension system including a lower arm which is A-shaped, and an upper arm of a double joint type. A ball joint can be used in place of the rubber bush joint 24₄, 24₇ supporting the lower end of the suspension spring 16₄. In addition, in place of the stabilizer 22₆, a radius rod can be also used as the restraining arm. Further any spring other than the coil spring, the torsion bar and the leaf spring can be used as the suspension spring 16₄.

Although preferred embodiments of the present invention have been described, it will be understood that the present invention is not limited to these embodiments, and various modifications in design can be made without departing from the spirit and scope of the invention. For example, the present invention is applicable to any suspension system, if it is used for a steered wheel, whether or not the steered wheel is a driven wheel. The scope of the invention is indicated by the appended claims, rather than by the foregoing description. 

What is claimed is:
 1. A suspension system for a steered wheel, comprising:a knuckle for steerably supporting the steered wheel about a king pin axis; upper and lower arms pivotally supported on a vehicle body and connected at free ends thereof to upper and lower portions of said knuckle, respectively; a link mechanism including a first substantially vertically extending rod connected to the knuckle at a location more inward of the vehicle body than said king pin axis, and a second rod connected at one end thereof to said first rod and at the other end to at least one of the vehicle body and the lower arm; said link mechanism being resiliently deformed during a steering operation to an extent corresponding to the steering operation; and a resilient means connected to said link mechanism for exhibiting a resilient force repulsive to deformation of said link mechanism So as to apply a restoring torque to the steering knuckle.
 2. A suspension system for a steered wheel according to claim 1, wherein said resilient means comprises a stabilizer extending laterally of the vehicle body, and a free end of said stabilizer is connected to said second rod.
 3. A suspension system according to claim 2, wherein said stabilizer has one end thereof connected to said link mechanism, and an opposite end thereof connected to another link mechanism for another steered wheel.
 4. A suspension system for a steered wheel according to claim 1, wherein said resilient means comprises a damper for damping vertical movement of said knuckle, and a lower end of said damper is connected to said knuckle through said first rod and to one of the vehicle body and the lower arm through said second rod.
 5. A suspension system for a steered wheel according to claim 1, wherein said resilient means comprises a suspension spring, said second rod is an A-shaped arm, said other end of the second rod is pivotally supported, at two points, to said vehicle body, and said suspension spring is supported by said link mechanism.
 6. A suspension system for a steered wheel according to claim 1, wherein said resilient means comprises a suspension spring, said second rod is an I-shaped arm, said other end of the second rod is pivotally supported at one point, to said vehicle body, the suspension further comprises a restraining arm pivotally supported on the vehicle body, said restraining arm is connected at an end thereof to said I-shaped arm, and said suspension spring is supported by said link mechanism.
 7. A suspension system for a steered wheel according to claim 1, wherein said resilient means comprises a suspension spring which is supported at one end thereof on the vehicle body, and a tip end on the other end of the suspension spring is supported on a tip end of said first rod.
 8. A suspension system according to claim 1, wherein the king pin axis as established by the suspension system is set to a very small value near zero relative to vertical.
 9. A suspension system according to claim 1, wherein the king pin axis as established by the suspension system is zero.
 10. A suspension system according to claim 1, wherein said second rod extends substantially horizontally.
 11. A suspension system according to claim 1, wherein said second rod extends laterally with respect to the vehicle body.
 12. A suspension system according to claim 1, wherein the steered wheel is connected to a steering mechanism, said link mechanism is deformed during operation of the steering mechanism, and said resilient repulsive force of said resilient means applies a restoring torque to the steering mechanism.
 13. A suspension system according to claim 1, further including a spring and damper unit having an upper end connected to the vehicle body and a lower end connected to said lower arm.
 14. A suspension system according to claim 1, wherein said resilient force exhibited by and said restoring torque applied by said resilient means correspond to an extent of deformation of said link mechanism.
 15. A suspension system for a steered wheel, comprising:a knuckle for steerably supporting the steered wheel about a king pin axis; upper and lower arms pivotally supported on a vehicle body and connected at free ends thereof to upper and lower portions of said knuckle, respectively; link means for operatively connecting said knuckle to the vehicle body and for being resiliently deformed during a steering operation of the steered wheel; and resilient means connected to said link means for exhibiting a resilient force repulsive to the deformation of said link means so as to apply a restoring torque to the steering knuckle through the link means.
 16. A suspension system according to claim 15, wherein said resilient means accumulates said resilient repulsive force therein with deformation of said link means.
 17. A suspension system according to claim 15, wherein said link means is connected to a portion of said knuckle located more inwardly of the vehicle body than said king pin axis.
 18. A suspension system according to claim 15, wherein said resilient means exhibits a resilient force repulsive to the deformation of said link means in a vertical direction, and said link means is adapted to be deformed primarily in the vertical direction.
 19. A suspension system according to claim 15, wherein said link means includes a first rod extending substantially vertically, said first rod being connected to said knuckle at a location more inward of the vehicle body than said king pin axis, and said link mechanism including a second rod connected at one end thereof to said first rod and at the other end thereof to at least one of the vehicle body and the lower arm.
 20. A suspension system according to claim 15, wherein said resilient means comprises a stabilizer extending laterally of the vehicle body, and a free end of said stabilizer is connected to said link means.
 21. A suspension system according to claim 15, wherein said resilient means comprises a damper for damping vertical movement of said knuckle, and said damper has one end thereof connected to said link means.
 22. A suspension system according to claim 15, wherein said resilient means comprises a suspension spring having one end thereof connected to said link means.
 23. A suspension system according to claim 22, wherein said suspension spring forms an integral part of said link means.
 24. A suspension system according to claim 15, wherein said link means includes means for resisting deformation in a horizontal direction, and said resilient means exhibits said resilient repulsive force when said link means is deformed in a vertical direction.
 25. A suspension system according to claim 15, wherein a steering mechanism is connected to said knuckle for steering the steered wheel, said link mechanism is mounted to said knuckle and deformed during steering operations of said steering mechanism, a king pin offset of the suspension system is set to a very small value near zero, relative to vertical and said repulsive force of said resilient means applies a restoring torque to the steering mechanism.
 26. A suspension system according to claim 15, further including a spring and damper unit having an upper end connected to the vehicle body and a lower end connected to said lower arm.
 27. A suspension system according to claim 15, wherein said link means is resiliently deformed to an extent corresponding to said steering operation during said steering operation.
 28. A suspension system according to claim 15, wherein said resilient force exhibited by and said restoring torque applied by said resilient means correspond to an extent of deformation of said link means. 